The invention relates generally to water screens and, more particularly, to traveling water screen systems with boot seals.
Water drawn into an industrial plant from a lake or river must be filtered to prevent debris from fouling equipment and causing damage. Traveling water screens are used to filter out and remove debris and fish from an influent channel before the debris can enter the plant or fish impinged on the upstream face of the screen die. A typical traveling water screen comprises a motor-driven screen, such as a foraminous conveyor belt, extending laterally across the width of the channel and vertically from the bottom of the channel to a height above the level of the water to ensure that all the water flowing in the channel passes through the screen. The screen travels a circuitous path around a motor-driven head shaft above the level of the water and a lower idle shaft in a boot section of the water screen at the bottom of the channel. The screen travels upward along the upstream portion of its circuitous path and downward along the downstream portion. A series of lift elements, such as baskets, scoops, or flights, extending outward of the screen at periodic intervals along its length lift debris or fish trapped on the upward-moving upstream portion of the water screen out of the channel for disposal in the case of debris and safe transit in the case of fish. Seals prevent unfiltered water containing fish and debris from flowing into the boot section of the water screen system between the screen and the bottom of the channel. A rubber flap or a metal plate attached at one end upstream of the boot section and extending over the upstream lip of the boot section are used as boot seals. The flap or plate backflexes by contact with the upwardly advancing flight exiting the boot section, its downstream end sliding along the tip of the flight to maintain the seal. Once the flight passes, the flap or metal plate, biased against the upward advance of the water screen, returns to its unflexed, sealed position with its downstream end close to the upstream face of the screen. While these seals form a seal with the tips of the flights, they do not form a seal at the side edges of the flights without custom modification. Furthermore, the biased metal plate seal allows the water screen to be advanced in a single direction and can be damaged if the water screen's direction of motion is reversed.